Neurotransmitters and their functions

How chemicals work within the neuron cells

1. Neurotransmitters
and their Functions
Master Program| Post Graduate
MS Psychiatric Nursing, 2
nd
Sem2020-21
IAU Faculty | Dr. James M. Alo

2. A neurotransmitter
•is a chemical substance that is released from a nerve cell and then
transmits an impulse from a nerve cell to its target. A target can be
another nerve, muscle, organ, or other tissue.
•It basically works as a messenger. They are produced in the cell body
of the neuron and transported to the axon terminal. They are stored
in vesicles.

3. Mechanism of action
•They are released from the
presynaptic terminal. After release,
they cause depolarization of the
terminal membrane which ultimately
causes activation of voltage-gated
Ca2+ channels.
•After activation of channels, there is
an influx of Ca2+ ions which cause
conformational changes.
•As a result, there is a fusionof the
vesicle to the plasma membrane and
there is the release of
neurotransmitters at the synaptic cleft

4. •Once released neurotransmitters diffuse
through the synaptic cleft.
•There they normally bind to the specific
receptors on the postsynaptic neuron
membrane. The action potential is created at
axon hillock and as a result, the
neurotransmitter is released which then
sends a message to its target.
•After performing its function,
neurotransmitter has different fates. It can
diffuse out of the synaptic cleft, it may be
taken the back up into presynaptic terminal
through transporter molecules or enzymes
metabolizeit inside synaptic cleft.

5. •Calcium (Ca2+) plays an important role in
the processof neurotransmitter release.
•When Ca2+ channels are blocked,
neurotransmitter release is inhibited.
•A neurotransmitter behaves in 2 ways:
•excitatoryincreases the chances of action
potential generated.
•Inhibitory: decreases the chances of action
potential generated.

6. Types of Neurotransmitter
-The type of neurotransmitter depends on the type of synapses utilized.
•The synaptic cleft, presynaptic
terminal, and receiving dendrite of
the next cell together form a junction
known as the synapse
•There are different types of synapses
but
•they all transmit messages of two types.
•Type I synapses: excitatory
•Type II synapses: inhibitory.
•These types vary in appearance and
location

7. Type I synapses:
•Location: Dendrite spine or shafts
•Characteristic feature: round synaptic vesicles
•Examples: Neurotransmitters that use these synapses are
Acetylcholine Epinephrine,Glutamate, Histamine, dopamine

8. Type II synapses
•Location: cell body.
•Characteristic feature: flattened
vesicles
•Examples: Some Neurotransmitters
that use these synapses are Serotonin,
GABA, Glycine.
•The neurotransmitter release
mechanisms are impaired in many
diseases like Schizophrenia,
Depression, Alzheimer's disease

9. Neurotransmitter systems
-Five majorneurotransmitter systems are
operating in the brain.
•Acetylcholine system
•Dopamine system
•Noradrenaline system
•Histamine system
•Serotonin system

10. Functions of Neurotransmitters
•Neurotransmitters play an
important role in a wide variety
of both physical and
psychological functions.
•There are hundreds of
neurotransmitters. Important
ones are detailed here:

11. Norepinephrine
•is the main neurotransmitter of the sympathetic nervous system.
•It has two forms. It is also released as a hormone and causes blood
vessels to contract and heart rate to increase.
•The basic function of norepinephrine as a neurotransmitter is to
mobilizethe brain and body for action.
•It is responsible for fight and flight response . It plays an important
role in wakefulness. It regulatescircadian rhythm and feeding
behavior. Along with dopamine, it plays a role in cognitive control and
working memory.

12. •It maintains energy homeostasis.
•It has a role in medullary control of respiration, negative emotional
memory and perception of pain.
•It has a minor role in the reward center. Deficiency of norepinephrine
can cause attention deficit hyperactivity disorder (ADHD), depression,
and hypotension.
•excess of norepinephrine can cause aches and pains, headache,
tachycardia, palpitations, sweating, paleness, anxiety, and a drop in
blood glucose. When sympathetic activity elevates for a long
duration, it may cause weight loss

13. Acetylcholine
•is the most abundantneurotransmitter in the human body found
both in CNS and PNS.
•It causes muscles to contract thus playing a role in all movements of
the body.
•It activates pain responses and regulates endocrine and REM sleep
functions.
•It is involved in regulating emotion, mood, learning, motivation and
short-term memory. It plays a minor role in the reward center.
•Low-level acetylcholine can lead to myasthenia gravis, which is
characterized by muscle weakness. Alzheimer's disease is
characterized by memory loss and in later stages inability for self-
care.

14. •It is caused by a loss of cells that secrete acetylcholine in the basal
forebrain. Excess of acetylcholine may cause signs and symptoms of
both the nicotinic and muscarinic toxicity.
•All these include increased salivation, cramps, muscular weakness,
lacrimation, muscular fasciculation, paralysis, blurry vision, and diarrhea.

15. Dopamine
•key neurotransmitter in our actions and
relationships.
•It has a significant role in arousal, aversion,
cognitive control, and working memory.
•It is involved in motivational salience, motor
function, and control. It is a primary
mediator of positive reinforcement and
reward center.
•It is responsible for sexual arousal, orgasm,
and refractory period

16. •Low levels of dopamine can cause Parkinson’s disease which is
characterized by a tremor. Further distinguishing features are slow
movements, rigid muscles, impaired posture and balance, loss of
automatic movements, speech and writing changes.
•It is caused by the loss of dopaminergic neurons in basal ganglia.
Schizophrenia is another example. If there is an excess dopamine
then it will lead to diseases like Tourette’s syndrome which is
characterized by repetitive tics

17. GABA
•is an inhibitory neurotransmitter that
is present abundantly in the neurons
of the cortex. The role of GABA is to
inhibit the activity of the neurons.
•It plays a role in motor and cortical
functions. It also regulates anxiety.
Alcohol is believed to cause its effects
by interacting with the GABA receptor.
•Low levels of GABA can lead to
hyperactivity and causes conditions
like epilepsy, seizures or mood
disorders.ExcessGABA can lead to
hypersomnia or daytime sleepiness.
•GABA affects on the body are
significant in pharmacology as by
increasing the level of GABA, we can
treat epilepsy and calm the trembling
of people suffering from Huntington’s
disease.
•Many medications interact with GABA
neurotransmission causing relaxation,
pain relief, stress, and anxiety
reduction, lower blood pressure, and
improved sleep

18. Serotonin
•important neurotransmitter in
the human body. It regulates
mood, our social behavior, sleep,
memory, and sexual desire.
•It is called the body's natural
feel-good chemical.
•Serotonin plays a role in bowel
function.
•Our intestines produce more
serotonin if we eat something
irritating or toxic to our digestive
system. The extra serotonin helps
move the affected food along so
it’s expelled from our body quickly.
•After an injury, platelets secrete
serotonin that causes
vasoconstriction which helps in the
blood-clotting process

19. •Low levels of Serotonin can cause anxiety, depressed mood,
aggression, impulsive behavior, suicidal thoughts, and insomnia.
Generalized anxiety disorder involves an imbalance of serotonin.
•High-level serotonin is associated with osteoporosis. Excess serotonin
can cause Serotonin syndrome is characterized by restlessness,
confusion, tachycardia, and hypertension. A patient can present with
dilated pupils, loss of muscle coordination, muscle rigidity, heavy
sweating, and diarrhea.
•Serotonin is significant in pharmacology as a major treatment of
anxiety and depression is dependent on the use of selective serotonin
reuptake inhibitors. They inhibit the re-uptake of serotonin from
synaptic gaps and increase neurotransmitter action which in turn
alleviates depressive symptoms.

20. Glutamate
•the most abundant excitatory
neurotransmitter in the vertebrate
nervous system.
•It helps in cognitive function,
memory, and learning. Glutamate
is a precursor for GABA. Glutamate
plays an important role in brain
development.
•The brain appears to need glutamate
to form memories. Glutamate plays a
significant role in muscle function.
•Glutamate plays the main function in
producing energy and the production
of supporting glutathione during
exercise.
•Glutamate delay muscular dystrophy
in animals deficient in vitamin D

21. •Glutamate receptors are present on immune cells (T cells, B cells,
macrophages, and dendritic cells), which suggests that glutamate
plays a role in both innate and adaptive immunity.
•Low brain levels of glutamate are associated with neurological and
psychiatric disorders. Glutamate levels were lower in schizophrenic
adults than healthy adults.
•Low levels of glutamate results in lack of energy, decreased appetite,
pale skin, headaches, tingling or numbness in the hands and feet,
Insomnia, exhaustion and concentration problems.
•High concentrations of glutamate in the brain have been associated
with neurological diseases such as schizophrenia, Parkinson's disease,
multiple sclerosis, Alzheimer's disease, stroke, and amyotrophic
lateral sclerosis.

22. Endorphin
•They are present in the whole
nervous system but the majority is
in the pituitary gland.
•They perform their actions by
interacting with opioid receptors.
They are of 3 types. Alpha
endorphin, Beta-endorphin,
Gamma endorphin.
•They can be called stress relievers.
.They alleviate pain and stress.
•Deficiency of endorphins can cause
depression and stress. Obsessive-
compulsive disorders can also
occur.
•Excess of endorphins can create
feelings of euphoria, increased
appetite, and sexual drive.
•Endorphins are important in
pharmacology as most of the pain-
killers actby mimicking the
endorphin mechanism.

23. Conclusion
•Neurotransmitters have a wide variety and mechanism of actions.
They play a significant role in our daily activity both physical and
psychological. Any impairment in their functions can lead to diseases.

24. References
https://www.d.umn.edu/~jfitzake/Lectures/DMED/NeuralCommunication/Neurotransmission/TransmitterRelease.html
https://www.britannica.com/science/neurotransmitter
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548657/
https://www.verywellmind.com/what-is-acetylcholine-2794810
https://thebrain.mcgill.ca/flash/i/i_01/i_01_m/i_01_m_ana/i_01_m_ana.html
https://www.verywellmind.com/what-is-serotonin-425327